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An exploratory investigation of the equilibrium phase behavior of binary blends of various polycarbonates with polystyrene (PS), poly(methyl methacrylate) (PMMA), bisphenol A polycarbonate (BPA-PC), and tetramethylbisphenol A polycarbonate (TMPC) is described. The variations in polycarbonate structure primarily involved substitutions onto the phenyl rings in two or four of the available positions and changing the connector group between the two phenyl rings, or both, of the bisphenol monomer. Polar connector groups promote favorable interactions with PMMA while ring substitution with methyl groups improves miscibility with PS. Other structural changes in the connector group or on the phenyl rings can act against the miscibility of polycarbonates with PMMA or PS. A wide range of polycarbonates was found to be miscible with BPA-PC and TMPC. The effect of PMMA and PS molecular weight on the miscibility of blends with selected polycarbonates wets used to obtain more detailed information about their interactions. The use of this information to design useful polymer blends is discussed.

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Dynamic mechanical and gas transport properties for homogeneous homopolymer blends and random copolymers of bisphenol‐A and tetramethyl bisphenol‐A polycarbonates (PC‐TMPC) were determined. The gas transport measurements were performed at 35°C for the gases He, H2, O2, Ar, N2, CH4, and CO2. The results show that the copolymers have lower permeability, apparent diffusion, and solubility coefficients than the blends. Permeability coefficients for blends follow a semilogarithmic ideal mixing rule while copolymers exhibit negative deviations from this. Specific volume measurements show that the free volume available for gas transport is slightly larger in copolymers than in blends of the same composition. These apparently contradictory results may relate to the differences in local mode chain motions observed for the copolymer and blend series. The γ relaxation processes in PC and TMPC seem to operate independently in the blends (no intermolecular coupling) while there is clear evidence for intramolecular coupling in the copolymers. © 1992 John Wiley & Sons, Inc.

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